Lewistown, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

336
FXUS65 KTFX 010532
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1132 PM MDT Mon Jun 30 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Warm temperatures expected Tuesday and Wednesday with highs in
   the 90s for most lower elevation locations.
 - Showers and thunderstorms return tomorrow, mainly south of
   I-90 and spread northward on Wednesday.
 - Shower and thunderstorm chances linger through the end of the
   week, even as temperatures cool to more seasonable levels.

&&

.UPDATE...
/Issued 754 PM MDT Mon Jun 30 2025/

Evening satellite and radar reveals a shower or two in Beaverhead
county. Otherwise the remainder of the region is seeing little to
no cloud cover this evening. The showers will dissipate over the
next couple hours, allowing for a benign overnight and start to
Tuesday.

Heading into Tuesday afternoon, deep inverted-V profiles will
support gusty outflow winds from any thunderstorms that form.
Areas most favored for a thunderstorm are along and south of I-90,
with areas on the plains seeing little to no chance for a shower
or thunderstorm.

The forecast for the remainder of the night is on track, hence no
updates will be posted this evening. -AM

&&

.DISCUSSION...
/Issued 754 PM MDT Mon Jun 30 2025/

 - Meteorological Overview:

With upper level ridging building across the Northern Rockies
early this week, temperatures will be on the increase over the
next few days. After highs just shy of or just over 90 today,
most lower elevation locations will see highs in the low to mid
90s Tuesday and Wednesday. Even with this ridge, a few showers and
thunderstorms will manage to pop up tomorrow, mainly south of
I-90. Showers and storms are likely to be more widespread on
Wednesday as an upper level trough begins to push ashore of the
west coast, helping to push some cooler air aloft as low level
moisture tries to sneak in from the east. Gusty winds and small
hail will be possible either day thanks to some weak shear and a
deep boundary layer.

The upper level ridge will gradually flatten out through the
second half of the week, which will allow temperatures to fall but
also result in near daily chances for showers and thunderstorms,
including on Independence Day.

 - Forecast Confidence & Scenarios:

Storms Tuesday and Wednesday: At the moment, confidence on
coverage and strength of shower and thunderstorm activity is low
to medium (30-50%), as the amount of moisture and shear needed for
storm development and maintenance remains on the low side.
However, if storms do manage to develop, a few of the storms may
produce some gusty outflow winds in excess of 50 mph on Tuesday
across Southwestern Montana, and this threat expands to include
the Plains on Wednesday. Wednesday is slightly more certain, but
the timing of the arrival of upper level forcing may be slightly
too late to allow for storms to become organized enough to produce
anything more than an isolated outflow should they collapse.
Ludwig

&&

.AVIATION...
01/06Z TAF Period

The main concern for the TAF period will be isolated to scattered
showers and thunderstorms Tuesday afternoon along and south of
the I-90 corridor. A few strong storms will be capable of
producing gusts in excess of 45kts. Everywhere else, calm winds
and an increase in cloud cover Tuesday evening. -Wilson

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  56  93  58  93 /   0   0   0  20
CTB  51  88  55  91 /   0   0   0  10
HLN  58  95  58  89 /   0   0  10  40
BZN  53  96  55  93 /   0  10  20  30
WYS  41  86  45  83 /   0  20  20  40
DLN  52  90  52  87 /   0  20  20  40
HVR  53  95  58  98 /   0   0   0  10
LWT  54  88  58  91 /   0   0  10  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
http://www.weather.gov/greatfalls